MELK is a really good spot to know about downtown- they have very high quality espresso-based drinks and lots of other little goodies. Good branding, too. A really good place to have a casual meeting or grab a latte on the go. Their only downside is rather limited seating though so don't assume that you will have a place to work or meet with several people.
MELK is also the most convenient place to find Detour beans in the downtown area, so come stock up.